Adhesive additive for a water lacquer

ABSTRACT

Adhesion additive for an aqueous paint, which comprises at least one binder and/or at least one pigment and/or filler and also at least one halogenated polyolefin (HPO), water, up to 25% by weight of solvents and, if desired, additives customary for aqueous paints. By virtue of the adhesion additive it is possible to apply paint coatings directly to plastic substrates without a primer.

The invention relates to an adhesion additive for an aqueous paint, to acurative for an aqueous paint, to the use of the adhesion additive forpreparing an aqueous paint, to the use of the curative for preparing anaqueous paint, to an aqueous paint which comprises the adhesion additiveand/or the curative, to the use of the aqueous paint for paintingplastic substrates and to a plastic part having a paint coating.

In industry today the use of plastic moldings which possess a paintcoating is on the increase. This relates in particular to plastic partson motor vehicles, such as bumpers, protection strips, spoilers, wheelarch linings and side sills. These parts are increasingly beingmanufactured from plastics with a polypropylene (PP) fraction of up to100%. The plastic parts which are used together with metal parts,especially in the automobile industry, frequently receive a paintcoating in the same color as that possessed by the other metal parts.

At the present time these plastic moldings are first provided with aprimer and are then painted first with a basecoat in the desired colorand subsequently with a clearcoat. Both solventborne and aqueous paintsare available for these purposes. In order to reduce the paintingoperation by the additional workstep of priming, special formulas havebeen developed for solventborne paints (EP 455 211), which allowadhesion of the paint directly to the plastic surface without anadditional primer coat. To date, however, it has not been possible touse water-based paints (WBP), which in view of the lower solventfraction of not more than 25% are preferable to the conventionalsolventborne paints from environmental, safety and health standpoints,for direct painting of plastic parts having a PP fraction of up to 100%.

It is an object of the present invention, accordingly, to provide anaqueous paint which allows the direct painting of plastic moldings, inparticular with a polypropylene fraction of up to 100%, and at the sametime possesses good adhesion to the plastic substrate, preferablycorresponding to that of a paint coating with priming beforehand. Thepaint coating ought in particular to produce the desired shade.

This object is achieved by means of an adhesion additive for an aqueouspaint, comprising a binder and/or a pigment and/or a filler, and alsohalogenated polyolefins (HPO), water and solvents, and also additivescustomary for aqueous paints, in accordance with independent claim 1.

A further achievement consists in the provision of a curative for anaqueous paint in accordance with independent claim 13.

The object is likewise achieved by, an aqueous paint in accordance withindependent claim 15 and also by an aqueous paint in accordance withindependent claim 17.

Advantageous developments are specified in the dependent claims. Thewording of all the claims is made by reference to the content of thedescription.

The adhesion additive of the invention for an aqueous paint contains0.1% to 40% by weight of at least one binder (calculated as solids)and/or 0.1% to 45% by weight of at least one pigment and/or filler andalso 0.5% to 30% by weight of at least one halogenated polyolefin (HPO),calculated as solids, and 0% to 80% by weight of water, 0% to 25% byweight of solvents, and, if desired, further additives customary foraqueous paints. The percentages indicated above, inclusive of theadditives, add up in total to 100% by weight.

The pigments and/or fillers are generally solids. Accordingly thefraction of pigments and/or fillers refers to the fraction calculated assolids.

The advantages of the invention are among others that by adding theadhesion additive conventional aqueous; paints can be used directly, asthe first coat, for painting plastic surfaces. As a result there is noneed for an additional workstep in painting, i.e., priming, in the caseof plastic substrates, which are very widespread particularly in theautomobile industry. Moreover, the invention allows wet-on-wet painting.This results in substantial savings in terms of time expended, materialsexpended and costs.

With conventional aqueous paints it is necessary to carry out a primingstep and possibly an intermediate sanding, as a result of which, inpainting operations, there is a time-consuming workstep which mustgenerally be carried out manually. The use of the aqueous paint of theinvention as a refinish paint makes it possible, to do away with thepriming and intermediate sanding of the surface to be painted.

In one embodiment of the invention the fraction of the binder(calculated as solids) is, advantageously 1% to 30% by weight,preferably 8% to 20% by weight and in particular 10% to 12% by weight.

The binder of the adhesion additive of the invention may be :a binderbased on acrylic resins, melamine resins and/or polyurethanes. In onepreferred embodiment the binder is a polyurethane resin.

The fraction of pigment and/or filler can in one embodiment be 0.1% to30% by weight, preferably 5% to 20% by weight, in particular 13% to 17%by weight.

In one particular embodiment of the invention the pigment is aconductive pigment.

The halogenated polyolefin (HPO) according to one preferred embodimentis a chlorinated polyolefin (CPO). It is, however, also possible to useother halogenated polyolefins, especially fluorinated polyolefins (FPO)or brominated polyolefins (BPO). In one particularly preferredembodiment the chlorinated polyolefin is a chlorinated polypropylene. Itis also conceivable to use other chlorinated polyolefins.

According to one embodiment the fraction (calculated as solids) of thechlorinated polyolefins a (CPO) is advantageously 1% to 20% by weight,preferably 3% to 10% by weight, in particular 6% to 8% by weight andwith particular preference about 7% by weight.

In one advantageous version the chlorinated polyolefin is a polyolefinhaving a chlorine content of 0.5% to 45% by weight, preferably 5% to 30%by weight, more preferably 10% to 20% by weight and in particular about16% by weight, based on the solids content of the chlorinatedpolyolefins.

The molecular weight of the chlorinated polyolefins (CPO) is preferably5,000 to 200,000 g/mol, preferably 10,000 to 170,000 g/mol, inparticular 20,000 to 100,000 g/mol, with particular preference 30,000 to60,000 g/mol.

The fraction of water in the adhesion additive of the invention isadvantageously 20% to 80% by weight, preferably 40% to 70% by weight, inparticular about 60% by weight.

The adhesion additive of the invention may also include a fraction ofsolvents. By solvents are meant here, in the context of the presentinvention, organic solvents. Advantageously the fraction of solvents is1% to 20% by weight; preferably 2% to 10% by weight and in particularabout 5% by weight. In one embodiment the solvents are glycol ethers andwhite spirit.

Since the CPO is frequently soluble only in organic solvents, thesolvent of the CPO is in particular, preferably, xylene, toluene and/orpetroleum fractions, especially xylene. In further embodiments mixturesof solvents are also conceivable. It is also possible to use a mixtureof solvent and water. In one preferred embodiment the CPO is soluble inwater.

A further aspect of the invention embraces a curative for an aqueouspaint which comprises at least one halogenated polyolefin, (HPO). Thehalogenated polyolefin (HPO) is preferably a chlorinated polyolefinhaving a chlorine content of 0.5% to 45% by weight, preferably 5% to 30%by weight, more preferably 10% to 20% by weight and in particular about16%, based on the solids content of the chlorinated polyolefins. Themolecular weight of the chlorinated polyolefin in the curative ispreferably 5,000 to 200,000 g/mol, more preferably 10,000 to 170,000g/mol, in particular 20,000 to 100,000 g/mol, with particular preference30,000 to 60,000 g/mol. The chlorinated polyolefin according, to onepreferred embodiment can be a chlorinated polypropylene. It isconceivable, however, to use other chlorinated polyolefins as well.

The invention further comprises an aqueous paint which comprises atleast one basecoat customary for aqueous paints and also at least oneadhesion additive of the invention. The weight ratio of adhesionadditive to basecoat in the aqueous paint of the invention is 5:95 to95:5. Preferably the weight ratio is between 30:70 to 50:50. In onepreferred embodiment the weight ratio of adhesion additive to basecoatis 50:50. In one particularly preferred embodiment the, weight ratio ofadhesion additive to basecoat is 30:70.

According to one embodiment the aqueous paint of the invention is aone-component paint. It is also possible for it to be atwo-component-paint. A two-component paint for the purposes of theinvention comprises a curative as well as the aqueous paint of theinvention. The curative can be a commonly used curative and/or acurative which comprises an HPO.

The amount of the curative is advantageously 0.5%.to 25% by weight,preferably 1% to 15% by weight, in particular about 5% by weight. In oneparticular embodiment the weight ratio of adhesion additive to basecoatto curative is 50:50:5. In another embodiment the weight ratio ofadhesion additive to basecoat to curative is 30:70:5.

The invention further embraces the use of the adhesion additive of theinvention for preparing an aqueous paint, in particular an aqueous paintintended for painting plastic substrates.

The invention further embraces the use of the curative of the inventionfor preparing an aqueous paint, in particular an aqueous paint intendedfor painting plastic substrates.

The invention further embraces the use of the aqueous paint of theinvention for painting plastic substrates, especially for painting motorvehicle parts.

The plastic substrates are preferably parts which contain apolypropylene fraction of up to 100% by weight. It is also conceivable,however, for the plastic substrates to be composed of at least one othermaterial, preferably a polymeric material.

Advantageously the plastic substrates for painting are flamed on thesurface by means of a flame, preferably a gas flame, immediately beforethe aqueous paint coat is applied. This removes impurities on thesurface of the substrate, especially release agent residues, and,particularly through the introduction of polar groups, allows theaqueous paint to adhere to the plastic surface, especially thepolypropylene surface. The flame is in particular a blue oxidizingflame.

It is also conceivable for the plastic substrates to be cleaned prior toflaming with a degreasing agent to remove fatty residues on the surface,before the aqueous paint of the invention is applied.

Application of the aqueous paint to the plastic substrate may take placefor example by means of painting guns.

The invention further embraces a plastic part with a paint coating whichcomprises at least one adhesion additive of the invention.

In the text below the adhesion additive of the invention and also theaqueous paint according to the present invention are illustrated bymeans of detailed description of particular embodiments and also throughexamples. In these examples, individual features of the invention may beactualized alone or in combination with other features. The examplesdescribed serve merely for elucidation and for better understanding ofthe invention and should not be understood in any way whatsoever to berestrictive.

EXAMPLES

a) Preparation of an adhesion additive (the percentages below relate ineach case to % by weight of the commercial forms of the raw materialsemployed):

First of all 15% of a binder in the form of a polyurethane resin.(Daotan, 32% in water, VTW 1237, Solutia GmbH & Co. KG) are charged to amixer. Subsequently the following raw materials are added individually,slowly, with stirring using a toothed disk; in the course of theaddition the temperature ought not to exceed 40° C.: 0.4% of adispersing assistant (Amp-90, Angus-Chemie GmbH), 2% of demineralizedwater (Herkommer and Bangerter GmbH & Co.), 1% white spirit (Testbenzin145/200, Brenntag Chemiepartner GmbH), 0.5% of defoamer (Addcitol VXW4973, Solutia GmbH & Co. KG), 0.3% of dispersant: (Orotan 731-K 25%,Rohm & Haas Deutschland GmbH) and 4% of an antisettling agent (BENTONEEW, Rheox, Inc. USA). This mixture is stirred for about 5 minutes.

Then the following fillers/pigments are added individually, slowly, withstirring using a toothed disk: 4.5% of pigment (LUZENAC 10M2 talc,Luzenac Deutschland GmbH), 5% of filler (Blanc-Fix-Micro, SachtlebenChemie GmbH), 5% of a further filler (Omya BLS, Omya GmbH) and 0.5% ofan antisettling agent (Aerosil R 972, Degussa AG). The overall mixtureis stirred for about 5 minutes, in the course of which the temperatureought not to exceed 40° C. Subsequently the mixture is finely ground ina bead mill (particle size <20 μm). During the grinding operation aswell the temperature ought not to exceed 40° C. The fine-ground mixtureis removed from the bead mill, which is rinsed with 2% of demineralizedwater, which is added to the mixture.

Thereafter the following raw materials are added individually, slowly,with stirring using a toothed disk: 19.5% of binder (Daotan VTW 1237,32% in water, Solutia GmbH & Co. KG), 35% of a chlorinated polyolefin(Hardlen EH 202, 20% in water, Siber Regner GmbH), 1% of demineralizedwater, 0.3% of a surface wetting agent (Troysol LAC, Troy ChemicalCorporation), 1% of a glycol ether (butyldiglycol, BrenntagChemiepartner GmbH), 1% of a further glycol ether (DOVANOL DPnB,dipropylene glycol n-butyl ether, Dow Chemical Company), 0.5% of whitespirit (Testbenzin 145/200, Brenntag Chemiepartner GmbH) and 0.5% of adefoamer (Additol VXW 4973). The mixture is stirred for about 5 minutes.

Following this the viscosity is adjusted with 1% of thickener (VISCALEXHV 30, Ciba Spezialitätenchemie). The finished mixture is stirred for afurther 15 minutes.

b) Preparation of the aqueous paint:

One-component aqueous paint: 50 parts by weight of the water-based paint(Wörwag 104131) are introduced and 50 parts by weight of the adhesionadditive are added slowly with stirring using a toothless stirring disk,followed by stirring for a further 5 minutes.

Two-component aqueous paint: First of all 50 parts by weight of thewater-based paint (Wörwag 104131) are introduced and mixed thoroughly.Then, slowly, 50 parts by weight of adhesion additive are added withstirring using a toothless stirring disk, followed by stirring for afurther 5 minutes. A further 5 parts by weight of a curative (Desmodur N3368 SN, Bayer AG) are added to this mixture, giving an overall weightratio of 50:50:5 (basecoat:adhesion additive:curative)

c) Adhesion test:

The plastic substrate of polypropylene is first cleaned with adegreasing agent and then flamed with a manual flaming device having ablue oxidizing flame. Subsequently the one-component paint is appliedusing a painting gun to the polypropylene plastic surface. The paint isdried by flashing off at room temperature for about 5 minutes and then asecond paint coat, consisting of the water-based paint without adhesionadditive, is applied wet on wet, flashed off at room temperature forabout 10 minutes and then dried at 80° C. for about 10 minutes. As thefinal paint coat a clearcoat is applied, which is dried initially atroom temperature for about 10 minutes and then at 80° C. for about 45minutes.

With the painted surface a cross-cut test is carried out in accordancewith the standard EN ISO 2409.

Table 1 shows the results of the cross-cut test on a one-component (1 K)paint and on a two-component (2 K) paint on a flamed and also anunflamed 100% polypropylene plastic surface, using as example twoaqueous paints with a mixing ratio of adhesion additive to water-basedpaint of 50:50 and 30:70. respectively. The results without, adhesionadditive are also indicated as a reference.

1-26. (canceled)
 27. An adhesion additive for an aqueous paint,containing 0.1% to 40% by weight of at least one binder calculated assolids and/or 0.1% to 45% by weight of at least one pigment and/orfiller and 0.5% to 30% by weight of at least one halogenated polyolefin(HPO) calculated as solids and 0% to 80% by weight of water, and 0% to25% by weight of solvents, and optionally, further additives customaryfor aqueous paints; wherein the above-mentioned percentages by weightinclusive of the additives adding up to 100% weight.
 28. The adhesionadditive of claim 27, characterized in that calculated as solids thereare 5% to 30% by weight, preferably 8% to 20% by weight, in particular10% to 12% by weight of binder(s).
 29. The adhesion additive of claim27, characterized in that binders based on acrylic resins, melamineresins and/or polyurethanes are present.
 30. The adhesion additive ofclaim 27, characterized in that 0.1% to 30% by weight, preferably 5% to20% by weight, in particular 13% to 17% by weight of pigments and/orfillers are present.
 31. The adhesion additive of claim 27,characterized in that the pigment is a conductive pigment.
 32. Theadhesion additive of claim 27, characterized in that the halogenatedpolyolefin is a chlorinated polyolefin (CPO), preferably a chlorinatedpolypropylene.
 33. The adhesion additive of claim 32, characterized inthat calculated as solids the fraction of chlorinated polyolefins (CPO)is 1% to 20% by weight, preferably 3% to 10% by weight.
 34. The adhesionadditive of claim 32, characterized in that calculated as solids thefraction of chlorinated polyolefins is preferably 6% to 8% by weight, inparticular about 7% by weight.
 35. The adhesion additive of claim 32,characterized in that the chlorinated polyolefin is a polyolefin havinga chlorine content of 0.5% to 45% by weight, preferably 5% to 30% byweight, more preferably 10% to 20% by weight and in particular about 16%by weight, based on the solids content of the chlorinated polyolefins.36. The adhesion additive of claim 32, characterized in that thechlorinated polyolefin is a polyolefin having a molecular weight of5,000 to 200,000 g/mol, preferably 10,000 to 170,000 g/mol, inparticular 20,000 to 100,000 g/mol and with particular preference 30,000to 60,000 g/mol.
 37. The adhesion additive of claim 27, characterized inthat 20% to 80% by weight, preferably 40% to 70% by weight, inparticular about 60% by weight of water is present.
 38. The adhesionadditive of claim 27, characterized in that 1% to 20% by weight,preferably 2% to 10% by weight, in particular about 5% by weight ofsolvent is present.
 39. A curative for an aqueous paint, which comprisesat least one halogenated polyolefin (HPO).
 40. The curative of claim 39,wherein the HPO is a chlorinated polypropylene (CPO), preferably achlorinated polypropylene.
 41. An aqueous paint comprising at least onebasecoat customary for aqueous paints and at least one adhesion additiveof any one of the preceding claims, the weight ratio of adhesionadditive to basecoat being between 5:95 and 95:5.
 42. The aqueous paintof claim 41, characterized in that the weight ratio of adhesion additiveto basecoat is preferably between 30:70 and 50:50.
 43. An aqueous paintcomprising a curative of claim
 39. 44. The aqueous paint of claim 41,characterized in that it is a one-component paint.
 45. The aqueous paintof claim 41 characterized in that it is a two-component paint whichcomprises a curative.
 46. The aqueous paint of claim 45, characterizedin that the amount of the curative is 0.5% to 25% by weight, preferably1% to 15% by weight, in particular about 5% by weight.
 47. A plasticpart with a paint coating, characterized in that the paint coatingcomprises at least one adhesion additive of claim 27.